[Elecraft] APF (audio peaking filter) on the K3/K3S/KX3

[Bill Frantz]

I followed my interpretation of Wayne's instructions when trying 
to copy VP8SGI on 80M. I have an inverted V antenna with the 
peak at about 12 meters (44').

When I started, I could barely hear him. When I got the APF 
tuned in, I could hear him clearly, and actually managed to work 
him with 100W. I had to send my call 5 0r 6 times before AA7A, 
the op on the other end got it, but I could easily hear when he 
got it. To pull me out of the muck means he must be really good.

When it worked well for me, there were no signals near the DX, 
and it worked with less ringing than going to a 50 Hz DSP 
bandwidth. I find when the CW gets up above about 25 WPM, the 
ringing makes it more difficult to interpret, although honestly, 
30 WPM is well above my CW speed of competency. 15 is more like 
it for English text (W1AW practice).

On the other hand, if there are nearby signals -- and I am using 
a 2.1KHz roofing filter when I have APF on -- then narrowing the 
DSP to 50 or 100Hz with the 250Hz roofing filter seems to work better.

73 Bill AE6JV

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Bill Frantz        |"Web security is like medicine - trying to 
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